The most common argument I see in support of the TSA’s authority to require passengers to undergo screenings that would, in other circumstances, be considered a violation of their Constitutional rights, is that traveling by air is a privilege and not a right. Since travelers choose to travel by air and are not required to do so, it’s legal for the TSA to require them to submit to X-rays, pat downs, and any other screening procedures the TSA deems necessary before they may board a plane.

This is a good argument. In fact, it’s so good that it has allowed the TSA (and its privately operated predecessors) to operate for years in the face of frequent legal challenges and protests.

It’s also a dangerous argument: it sneakily undermines citizens’ Constitutional rights by declaring those rights to exist only within certain boundaries—boundaries that are defined by the government from whom those rights are supposed to protect us, and defined in a way that bypasses the checks and balances required by the Constitution.

Flying was once a luxury, in the same way that traveling by automobile was once a luxury. Fifty years ago, few people could claim that their livelihood or their well-being required them to travel by air. One hundred years ago, the same was true of cars.

Today, though, air travel is commonplace. Many people have jobs that require them—require them—to travel frequently across long distances. In a large country like the United States, without any ground-based high speed transit infrastructure to speak of, flying is often the only realistic option. A trip that takes hours by plane may take days by train or by car.

To a casual traveler who objects to being X-rayed or patted down, this may seem like a relatively easy choice. Take fewer trips, or budget more time and turn them into road trips. To someone who is required to travel as a condition of their employment, this choice isn’t so easy. Budgeting time for road trips isn’t likely to be an option. This person is faced with a more difficult choice: they can forfeit their civil liberties or they can find a new job.

It would be unwise to assume that the TSA will be content to limit their screenings to air travel. With a strong foothold in all of the nation’s airports, it’s only a matter of time before the TSA asserts the authority to require screenings for rail travel. If things continue in this vein, we’ll see mandatory TSA checkpoints on major interstate highways within the next thirty years (the justification: drivers don’t have to take the interstate).

One thing history has taught us is that people who willingly give up their freedoms rarely have an easy time getting them back. Nobody wants to make it easy for evildoers to smuggle weapons onto airplanes, but we need to find better solutions than the ones the TSA claims are necessary, and these solutions need to be balanced with the actual risks they’re intended to guard against.

Freedom makes a terrible currency. Using freedom to buy safety only leads to bankruptcy.